Creating event handlers.
Event handlers can be added in Nagios to take care of any specific event. It’s the way to tell nagios what is needed to be done in case a specific service alert is triggered.
Let’s say, an apache service monitoring is in place and it as per service check port 80 or 443 is unreachable i.e. the apache/httpd service went down.
Via event handler apache start command can be initiated from Nagios itself to make the service up.
This way events can be handled via Nagios.